Refining of petroleum oil



Patented Apr. 17, 1934 UNITED STATES PATENT No Drawing. Application May21, 1931, Serial No. 539,111

6 Claims. (01. 196-36) This invention relates to the treatment ofhydrocarbon oils and more particularly is directed to the treatment ofpetroleum distillates, especially those resulting from the conversion ofrelatively higher boiling hydrocarbons into lower boiling hydrocarbonsby treatment at elevated temperatures, commonly referred to as crackeddistillates, by subjecting the same while in vapor formto the action ofaqueous solutions of acid sulphates alone or in direct combination withsulphuric acid, to modify and regulate the reactions of the latter.

More particularly the invention relates to the treatment of the saidhydrocarbons while in vapor form with solutions containing sulphuricacid and a salt of an alkali metal such as the sulphates of sodium,potassium, ammonium and the like. Presumably, these salts are present asacid sulphates and it is desirable that they always be present in theform of the acid sulphate, preferably with excess sulphuric acid. Theuse of other salts such as the chlorides, acetates, nitrates, etc., ofthe alkali metals are contemplated in admixture with sulphuric acid,since to some extent and degree they are equivalent to the sulphates inthe presence of sulphuric acid.

Petroleum distillates, especially cracked distillates, containundesirable compounds, presumably of a highly unsaturated character,which render them unstable with respect to color, gumforming propertiesand knock rating. Such distillates tend to deposit polymer or gum-likesubstances while in storage, causing a drop in color which may renderthe product unsaleable. The development of gums may also prevent properoperation of the motor by plugging or gumming up the fuel lines,carburetor, valves and other parts of the motor. Other objectionablecompounds such as those of sulphur, nitrogen and the like may be presentin such distillates, and it is among the objects of this invention toremove, or reduce to a minimum, the objectionable substances present inpetroleum distillates.

One of the important and desirable developments in petroleum refining isthe direct production of a marketable distillate from the crackingprocess. Many attempts have been made to employ refining agents for thispurpose, particularly directed towards the use ofsulphuric acid which,for the most part, have been unsuccessful because they have failed totake into consideration the physical and chemical properties ofsulphuric acid under the-conditions of refining. The use of sulphuricacid as a refining agent antedates the' drillingcof the first oil wellin the United States but heretofore it has been successfully applied asa refining agent to petroleum and its products only while in the liquidstate.

'The following table taken from the 1913 edi-'- tion of the Manufactureof Sulphuric Acid and Alkali by Lunge, a standard work on the subject,shows the relationship between the boiling point and concentration ofsulphuric acid:

Table NO. I

Percent H2804 B. Pt. T.

From the above table it is evident that at; a given temperature and ateach temperature the sulphuric acid exists at a definite concentrationand that irrespective of the concentration of the sulphuric acid fedinto a system at a given temperature if it is more dilute than thatindicated by the concentration-for the corresponding temperature itwillconcentrate to the given concentration; also that for each set ofconditions there is acor-respondingminimum concentration. For example,if an approximately 8% solution of sulphuric acid is fed into a tower,the average temperature ofwhich isapproximately 360 F., neg+ lecti-ngthe partial pressures of the steam and oil vapors, the sulphuricacidintroduced will concentrate to approximately 75% and under thesetemperature conditions such aconcentr'a tion of sulphuric acid willimmediately attack and destroy the unsaturated hydrocarbons in theimmediate vicinity, resultingin an off-colored overhead product of highgum content: and in a charring of the derivatives of sulphuric acid inthe hydrocarbons, plugging up the column and rendering the processinoperative. The above indicates only approximately the conditionsexisting in the tower but is sufiicient to illustrate the trend anddirection of the reaction and explain Why previous attempts to refine inthe manner described have been unsuccessful.

It is well known that concentrations of sulphuric acid which may be evensubstantially nonreactive at ordinary temperatures are highly .de-

structive in their reactions at elevated temperatures. Hence, while itis desirable to treat petroleum distillates in the vapor state in orderto avoid the expense of redistilling the product, it is imperative thata method of treatment be provided which will enable one to definitelycontrol the concentration and consequently the rate and kind of reactionat the elevated temperatures of treatment. The present inventionaccomplishes this aim in a new and novel manner which will behereinafter more fully described.

In a specific aspect the invention comprises treating hydrocarbonvapors, especially cracked hydrocarbon vapors, with an aqueous solutioncontaining dissolved therein sulphuric acid and a sulphate of an alkalimetal which is presumably present in the form of the acid sulphate.

In effecting the operation of the invention hydrocarbon vapors from anysource, for example, direct from a cracking process, and in general froma distillation process, including vapors from atmospheric distillationor hydrocarbon vapors from rerun stills, may be passed counter-currentor concurrent to the solution containing the acid sulphate and thesulphuric acid. The treating solution may be introduced in the form of aspray atomized or otherwise introduced and employed in such manner as togive the most efficient contact of treating agent and vapors undergoingtreatment. Under some conditions the hydrocarbon vapors may be bubbledthrough a pool or pools of the treating agent, preferably feeding infresh reagent and withdrawing sludge continuously. In the countercurrentoperation the vapors may be withdrawn from the top of the treating towerand may be condensed or fractionated and condensed, preferablysubjecting the treated hydrocarbons to further treatment with alkaliesor combination washing and alkali to remove sulphur dioxide and possiblysome entrained treating agent. In the concurrent method of operation,the vapors, reflux condensate and sludge may be passed through aseparator, withdrawing the vapors and condensing as described, andseparately withdrawing the sludge and/or productsof reaction togetherwith unused treating agent and reflux condensate if present.

Aqueous solutions of the acid sulphates may be mixed with the aqueoussolutions of the sulphuric acid or aqueous solutions of the sulphates ofsodium, potassium or ammonium may be mixed with sulphuric acid,preferably having a substantial excess of sulphuric acid over thatrequired to produce the acid sulphate. Steam may be introduced into thecolumn during the treatment in order to assist in maintaining anequilibrium between the dissolved substances in the water, namely, theacid sulphate and sulphuric acid. The acid sulphates and part of theacid may be recovered by dilution of the acid sludge with water,heating, separating the oily sludge, and subsequent purification andevaporation of the aqueous solution.

The process may constitute a sole step in the refining of thehydrocarbons or may be combined with other treatments either appliedbefore or after the process of this invention. For example,

the vapors from the treating tower may be subsequently passed through afilter or series of filters containing inert filtering agents,adsorbents, solid alkalies, such as lime, caustic, or mixtures of these,and the like, catalytic materials such as metals and metallic oxides,solutions of alkalies, and the like. Preferably, the vapors arefractionated before passing to the treating stage and may befractionated after passing to the treating stage. Prior treatments ofthe hydrocarbons with other reagents, either in the vapor or liquidphase, or subsequent treatment of the condensed liquid may be applied.

For example, the condensed product may be neutralized by treatment withan alkaline solution or besweetened by treatment with plumbitesolutions, solutions of copper salts, or other metallic salts, alone orin combination with auxiliary chemical treatments with acids and thelike, orv with filtering agents such as fullers earth and like adsorbingagents.

As examples of the conditions of treatment and the results obtained bythe operation of the invention, the following are cited. All of theresults shown in the tables illustrate the treatment of a crackeddistillate from California stock.

The liquid recovery in the above treats varies between 98% and 99%,indicating very low losses during the treatment. The amount of reagentemployed varies with the conditions of treatment, the oil to be treated,and the results desired. The reagent may be reused and or recovered forreuse.

Table III 010. so 11. Per- Run Percent per Tem. cent No. NH4HSO4 6 ffg gliter r. Gum sulo i phu oil 16.5 21.2 62.3 160 300 +23 23 0.37 lstpass35.3 37.5 27.2 145 300 +21 175 0. 39 2d pass 35.3 37.5 27.2 160 300 +2314 0.38 3d pass Table IV 3 21.7 I 25.7 52.6 120 310 30+ 8 0.33 4 ReusmgSOIIIItiOHS from (3) 205 300 +28 8 0.40

Lamp stability-+23 (Equivalent to 2 hours sunlight) Octane No.72

Bomb stability-No drop in 4 hours.

Air jet gum after oxidation-18 Color after oxidation+12 Octane No. afteroxidation70 The solution reused was from Run 3. It was filtered throughasbestos to remove as much suspended material as possible.

Run Nos. B and C show that good results can be obtained with lowerconcentrations of H2804. by increasing the time of contact.

The product from Run 3 after standing 10 days dropped in color to +28but only dropped five points more when exposed to the ultra violet lamp.The oxygen stability was also very good.

Run 4 shows that the solution can be used over again with good results.Further results have shown that it can be used many times especiallywhen make-up solutions of salts and acid are added.

The quantities of solutions used relative to the oil should besufficient to maintain good contact. Much smaller quantities give goodresults and repeated uses of non-regenerated solution is contemplated.Also, regeneration and/ or recovering of the acid sulphate (salts) andsulphuric acid is contemplated.

The above data illustrates that certain combinations and conditions oftreatment give better results than others. The results in Run Table No.2 show a color of the finished product of 30 plus Saybolt with a gumcontent of only 6 mgs. per 100 cc. The gum content of the originaluntreated cracked distillate of like boiling range exceeded 400 mgs. per100 cc. and the color was a dark reddish brown.

The sludge from the treating agent may be recirculated for furthertreatment to reduce the total percent of treating agent by volume of theoil treated to several percent. In the treatment of a Mid-Continentcracked distillate in the vapor phase employing approximately 3% of asolution containing approximately 20% of ammonium acid sulphate, 50% ofsulphuric acid, and 30% of water, a product of plus 30 color containingless than 10 mgs. of gum per 100 cc. of good color stability may beobtained, the raw distillate being dark brown in color and containing inexcess of 350 mgs. of gum per 100 cc. Similar results may be obtainedwith other types of oils.

Similar results may be obtained also with solutions containing sodiumsulphate and potassium sulphate with sulphuric acid as with ammoniumsulphate and others and the corresponding acid sulphate although theresults may vary in degree.

The concentrations of the acid sulphate and sulphuric acid may be variedto suit the particular conditions of treatment, particularlytemperatures; generally, the higher the temperature the higher theconcentration of sulphuric acid, and in general, the conditions arevaried dependcut on the results desired.

Inasmuch as there are many conditions of treatment and variables inrespect to the concentrations of dissolved salts and sulphuric acid,temperatures and the like, the above examples are illustrative only andare not to be construed as limitations upon the broad scope of theinvention.

I claim as my invention:

1. A process for refining hydrocarbon oil which comprises treating thesame in vapor phase with an aqueous sulphuric acid solution to which hasbeen added a water soluble sulphate, the amount of sulphuric acid in thesolution being in excess of that required to maintain the sulphate inthe form of the acid sulphate.

2. A process for refining hydrocarbon oil which comprises treating thesame in vapor phase with an aqueous sulphuric acid solution to which hasbeen added a normal water soluble sulphate, the amount of sulphuric acidin the solution being sufficient to convert the normal sulphate to theacid sulphate.

3. A process for refining hydrocarbon oil which comprises treating thesame in vapor phase with an aqueous sulphuric acid solution to which hasbeen added an alkali metal sulphate, the amount of sulphuric acid in thesolution being in excess of that required to maintain the sulphate inthe form of the acid sulphate.

4. A process for refining hydrocarbon oil which comprises treating thesame in vapor phase with an aqueous sulphuric acid solution to which hasbeen added an ammonium sulphate, the amount of sulphuric acid in thesolution being inexcess of that required to maintain the sulphate in theform of the acid sulphate.

5. A process for refining hydrocarbon oil which comprises treating thesame in vapor phase with an aqueous sulphuric acid solution to which hasbeen added a normal alkali metal sulphate, the amount of sulphuric acidin the solution being sufficient to convert the normal sulphate to theacid sulphate.

6. A process for refining hydrocarbon oil which comprises treating thesame in vapor phase with an aqueous sulphuric acid solution to which hasbeen added a normal ammonium sulphate, the amount of sulphuric acid inthe solution being suflicient to convert the normal sulphate to the acidsulphate.

JACQUE C. MORRELL.

